diff --git a/packages/Php/src/Rector/String_/StringClassNameToClassConstantRector.php b/packages/Php/src/Rector/String_/StringClassNameToClassConstantRector.php
index 22feb0661962..8a2fd4fdc87b 100644
--- a/packages/Php/src/Rector/String_/StringClassNameToClassConstantRector.php
+++ b/packages/Php/src/Rector/String_/StringClassNameToClassConstantRector.php
@@ -10,6 +10,7 @@
 use Rector\RectorDefinition\CodeSample;
 use Rector\RectorDefinition\RectorDefinition;
 use Rector\Util\RectorStrings;
+use ReflectionClass;
 
 /**
  * @see https://wiki.php.net/rfc/class_name_scalars
@@ -21,6 +22,16 @@ final class StringClassNameToClassConstantRector extends AbstractRector
      */
     private $classesToSkip = [];
 
+    /**
+     * @var string[]
+     */
+    private $sensitiveExistingClasses = [];
+
+    /**
+     * @var string[]
+     */
+    private $sensitiveNonExistingClasses = [];
+
     /**
      * @param string[] $classesToSkip
      */
@@ -80,7 +91,7 @@ public function getNodeTypes(): array
     public function refactor(Node $node): ?Node
     {
         $classLikeName = $node->value;
-        if (! $this->classLikeExists($classLikeName)) {
+        if (! $this->classLikeSensitiveExists($classLikeName)) {
             return null;
         }
 
@@ -91,7 +102,33 @@ public function refactor(Node $node): ?Node
         return new ClassConstFetch(new FullyQualified($classLikeName), 'class');
     }
 
-    private function classLikeExists(string $classLikeName): bool
+    private function classLikeSensitiveExists(string $classLikeName): bool
+    {
+        if (! $this->classLikeInsensitiveExists($classLikeName)) {
+            return false;
+        }
+
+        // already known values
+        if (in_array($classLikeName, $this->sensitiveExistingClasses, true)) {
+            return true;
+        }
+
+        if (in_array($classLikeName, $this->sensitiveNonExistingClasses, true)) {
+            return false;
+        }
+
+        $classReflection = new ReflectionClass($classLikeName);
+
+        if ($classLikeName !== $classReflection->getName()) {
+            $this->sensitiveNonExistingClasses[] = $classLikeName;
+            return false;
+        }
+
+        $this->sensitiveExistingClasses[] = $classLikeName;
+        return true;
+    }
+
+    private function classLikeInsensitiveExists(string $classLikeName): bool
     {
         if (class_exists($classLikeName)) {
             return true;
diff --git a/packages/Php/tests/Rector/String_/StringClassNameToClassConstantRector/Fixture/skip_sensitive.php.inc b/packages/Php/tests/Rector/String_/StringClassNameToClassConstantRector/Fixture/skip_sensitive.php.inc
new file mode 100644
index 000000000000..c614765ae38b
--- /dev/null
+++ b/packages/Php/tests/Rector/String_/StringClassNameToClassConstantRector/Fixture/skip_sensitive.php.inc
@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Php\Tests\Rector\String_\StringClassNameToClassConstantRector\Fixture;
+
+class SkipSensitive
+{
+    public function run()
+    {
+        return ['exception' => 'Exception'];
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Php\Tests\Rector\String_\StringClassNameToClassConstantRector\Fixture;
+
+class SkipSensitive
+{
+    public function run()
+    {
+        return ['exception' => \Exception::class];
+    }
+}
+
+?>
diff --git a/packages/Php/tests/Rector/String_/StringClassNameToClassConstantRector/StringClassNameToClassConstantRectorTest.php b/packages/Php/tests/Rector/String_/StringClassNameToClassConstantRector/StringClassNameToClassConstantRectorTest.php
index 9034d9acd470..c57661aea005 100644
--- a/packages/Php/tests/Rector/String_/StringClassNameToClassConstantRector/StringClassNameToClassConstantRectorTest.php
+++ b/packages/Php/tests/Rector/String_/StringClassNameToClassConstantRector/StringClassNameToClassConstantRectorTest.php
@@ -9,7 +9,11 @@ final class StringClassNameToClassConstantRectorTest extends AbstractRectorTestC
 {
     public function test(): void
     {
-        $this->doTestFiles([__DIR__ . '/Fixture/fixture.php.inc', __DIR__ . '/Fixture/skip_error.php.inc']);
+        $this->doTestFiles([
+            __DIR__ . '/Fixture/fixture.php.inc',
+            __DIR__ . '/Fixture/skip_error.php.inc',
+            __DIR__ . '/Fixture/skip_sensitive.php.inc',
+        ]);
     }
 
     protected function getRectorClass(): string